Antenna system



July 21, 1942. M KA ZIN v 2,290,371

ANTENNA SYSTEM Filed April 15, 1941 Fig. I

HIGH FREQUENCY APPjIQATUS I =1 =1l=1=, 5 1: G:' 1:: o-

PHASE CHANG/N6 NETWORK INVENTOR MART/N I64 7Z//V BYMZW ATTORNEY PatentedJuly 21, 1942 ANTENNA SYSTEM Martin Katzin, Washington, D. 0., assignorto Radio Corporation of America, a corporation of Delaware ApplicationApril 15, 1941, Serial No. 388,609

11 Claims.

The present invention relates to an improvement in directive antennasystems and, more particularly, to such of these systems as are commonlyknown by the term fish-bone antenna because of their physicalconfiguration. Such a fish-bone type of antenna, upon which the presentinvention is an improvement, is described in a Peterson Patent No.2,130,675, granted September 20, 1938.

An object of the present invention is to increase the effectivefrequency band coverageof a fish-bone antenna.

Another object of the present invention is the provision of anultra-high frequency traveling wave antenna having a uniform responseover a wide frequency range.

Still another object is the provision of a directive antenna operativeOver a wide range of operating frequencies.

Still a further object is the provision of a highly directive antennasuitable for the reception and/ or transmission of television.

The foregoing objects, and others which may appear from the followingdetailed description, are attained in accordance with the principles ofthe present invention by the provision of an elongated parallel wiretransmission line having lateral signal collectors coupled thereto atintervals along its length. The signal collectors may be of uniformlength or their length may taper along the length of the transmissionline in order to increase the effective band width of the antennasystem. The signal collectors are preferably not directly connected tothe transmission line but loosely coupled thereto as by seriescondensers or inductances so as not to load the transmission lineunduly.

In order to make the antenna uni-directional the'end of the transmissionline remote" from its connection to a receiver or other transducermeansa-nd which is directed toward a remote station with whichcommunication is to-be established is closed by a terminating resistorhaving a resistance equal to the surge impedance of the line. Atappropriate intervals along the length of the transmission line phasechanging networks are inserted therein to'overcome the effects of lowvelocity of signal propagation along the line compared with the velocityof signal-propagation in free space. The phase changing networks aredesigned to change the phase of signals. traveling along the line by 180degrees at the high frequency end of the band of signals and tochangethe phase progressively less toward the low frequency end of the band.The phase changing networks are arranged to have an impedance equal tothe surge impedance of the line regardless of the frequency and to haveno attenuation to the wave. 7

Although the antenna is, in this specification, described especiallywith reference to a receiving system, it is to be clearly understoodthat its use is not limited thereto since it may also be used fortransmitting purposes.

The present invention may be more fully understood by reference to thefollowing detailed description which is accompanied by a drawing inwhich Figure 1 illustrates schematically a simple embodiment of afish-bone antenna embodying the principles of the present invention andFigures 2 and 3 illustrate the details of phase changing networkssuitable for use in the an tenna system as shown in Figure 1.

Referring to Figure 1, there is shown a fishbone antenna comprising aclosely spaced twowire horizontal feeder line I' connecting highfrequency apparatus 2, conventionally shown in. box form, withexternally arranged antenna doublets 3, 3. These doublets are disposedalong the length of the feeder line I, there being preferably at leastsix to each wavelength of feeder line. The doublets may beoriented atany desired angle with respect to the plane of the earth depending uponwhether horizontally or vertically polarized signals are to be received.Figure 1 is terminated at its far end by its surge impedance Z of avalue equaling the surge impedance of the line I as loaded by theantenna doublets 3.

As shown in Figure 1,. the antenna is divided into two sectionsconnected end to end by the phasev changing network 5. More sections maybe used if greater directivity and sensitivity is desired. The phasechanging network 5 is designed to produce a change of 180 degrees ofelectrical phase in the feeder line for the highest frequencies to bereceived or transmitted and progressively less for lower frequencies.overall length of each section of the antenna projected upon a lineparallel to the direction of electromagnetic wave propagation issomewhat less than one-half wavelength less than its actual length dueto the fact that the energy traveling along transmission line I travelstherein more slowly than the wave is propagated through the ether. In atypical case the, phase velocity of the antenna feeder line I may be orof the velocity of the propagation in free space. The energy received bythe signal collectors 3 as the received wave progresses in. space overthe antenna from surge impedance Z to the receiver The.

2 produces incremental voltages in feeder line I which build up into asingle resultant voltage. Since these increments of voltage progressalong the feeder at a velocity slower than the velocity of thepropagation of the wave front in space, the resultant of the earliercomponents of voltage in the antenna feeder line tend to lag farther andfarther behind the space of the more recently induced increments until,without the interposition of the phase changing network 5, the resultantvoltage would begin to decrease rather than increase with the length ofthe antenna. However, the phase changing network 5 serves to turn thevoltage of the higher frequencies through an angle of 180 electricalphase so I that it may once again be directly added to all the voltagesdeveloped by the electric wave front passing by the collectors nearerthe high frequency apparatus Z. Therefore, an optimum building up of thevarious increments of voltage occurs for a wave front advancing in thedesired direction at the highest frequency for which the antenna isdesigned. For progressively lower frequencies less phase shift isintroduced by the phase changing network 5 and since there is less ldifference in wave velocity in feeder l and in free space for the lowerfrequency waves the energy representative of the lower frequencies willalso be added in an in-phase relationship throughout the length of theantenna. For the lowest frequencies for which the antenna is designedthe phase changing network 5 has substantially no phase shifting effectsince the difference in phase between the various increments of voltageof the wave in feeder l and in free space for the lower frequencies iscorrespondingly small. It is essential that the phase changing network 5have a surge impedance equal to the surge impedance of line I for allfrequencies for whichthe antenna is designed. Otherwise, reflectionswould be set up and the efficiency of the antenna would decreaserapidly. Also, the phase changing network 5 must impart substantially noattenuation to the wave as, otherwise, the.losses introduced by theinsertion of the phase changing network would more than counteract theadvantages obtained by its use. Phase changing networks which fulfillthese require ments are shown in Figures 2 and 3 of the drawing.

These networks have been completely described in the Bell SystemTechnical Journal for July, 1928, pages 529 and 530, and it is believedunnecessary to describe them in detail here.

Reference may be had to the above mentioned publication for design fordetails of the networks whereby the desired 180"phase shift at the highfrequency end of the spectrum to be received may be had.

While I have particularly shown and described several modifications ofmy invention, it is to be distinctly understood that my invention is notlimited thereto but that improvements within the scope of the inventionmay be made.

I claim:

1. A directive antenna system for a broad band of short waves comprisingtwo closely spaced substantially straight feeder conductors connected atone end to high frequency apparatus, a plurality of groups of antennaunits transversely coupled to said line, a phase changing networkinterposed between two groups of said antenna units for producing alongsaid feeder a reversal in phase of the highest frequency energy in saidconnected at one end to high frequency appa- .ratus, a plurality ofgroups of antenna units transversely coupled to said line, a phasechanging network interposed between two groups of said antenna units forproducing along said feeder a reversal in phase of the highest frequencyenergy in said band, said phase changing network having progressivelydecreasing effect with decreasing frequency and an impedance connectedacross the end of said line remote from said high frequency apparatus,said impedance having a value equal to the surge impedance of said lineas loaded by said antenna units, said phase changing network having aconstant impedance equal to the surge impedance of the line andsubstantially zero attenuation for all frequencies within the band.

3. A directive antenna system for a broad band of short waves comprisingtwo closely spaced substantially straight feeder conductors connected atone end to high frequency apparatus, a plurality of groups of antennaunits transversely coupled to said line, phase changing networksinterposed between successive groups of said antenna units for producingalong said feeder a reversal in phase of the highest frequency energy insaid band, said phase changing networks having progressively decreasingeffect with decreasing frequency and an impedance connected across theend of said line remote from said high frequency apparatus, saidimpedance having a value equal to the surge impedance of said line asloaded by said antenna units.

4. A directive antenna system for a broad band of shortwaves comprisingtwo closely spaced substantially straight. feeder conductors connectedat one end to high frequency apparatus, a plurality of groups of antennaunits transversely coupled to said line, phasechanging networksinterposed between successive groups of said antenna units for producingalong said feeder a reversal in phase of the highest frequency energy insaid band, said phase changing networks .having progressively decreasingeffect with decreasing frequency and an impedance connected .across theend of said line remote from said high frequencyapparatus, saidimpedance having a value equal to the surge, impedance of said line asloaded .by said antenna units, said phase changing networks having aconstant impedance equal to thesurge impedance of the line andsubstantially zero attenuation for all frequencies within the band.

5. A directive antenna system for a broad band of short waves comprisingtwo closely spaced substantially straight feeder conductors connected atone end to high frequency apparatus, a plurality of groups of antennaunits transversely coupled to said line, a phase changing networkinterposed between two groups of said antenna units for producing alongsaid feeder a reversal in phase of the highest frequency energy in saidband, said phase changing networks having progressively decreasingeffect with decreasing frequency.

6. A directive antenna system for a broad band of short waves comprisingtwo closely spaced substantially straight feeder conductors connected atone end to high frequency apparatus, a plurality of groups of antennaunits transversely coupled to said line, phase changing networksinterposed between successive groups of said antenna units for producingalong said feeder a reversal in phase of the highest frequency energy insaid band, said phase changing networks having progressively decreasingeffect with decreas ing frequency.

7. A directive antenna system for a broad band of short waves comprisingtwo closely spaced substantially straight feeder conductors connected atone end to high frequency apparatus, a plurality of groups of antennaunits transversely coupled to said line, a phase changing networkinterposed between two groups of said antenna units for producing alongsaid feeder a reversal in phase of the highest frequency energy in saidband, said phase changing network having progressively decreasing effectwith decreasing frequency, said network having a low and constantattenuation for all frequencies within said band.

8. A directive antenna system for a broad band of short waves comprisingtwo closely spaced substantially straight feeder conductors connected atone end to high frequency apparatus, a plurality of groups of antennaunits transversely coupled to said line, phase changing networksinterposed between successive groups of said antenna units for producingalong said feeder a reversal in phase of the highest frequency energy insaid band, said phase changing networks having progressively decreasingeffect with decreasing frequency, said networks having a low andconstant attenuation for all frequencies within said band.

9. A directive antenna system for a broad band of short waves comprisingan elongated signal collector connected at one end to high frequencyapparatus and the other end directed toward another station with whichcommunication is to be established, said collector being divided intoseparate sections, phase changing networks interposed between each twosuccessive sections for producing therealong a reversal in phase of thehighest frequency energy in said band, said phase changing networkshaving progressively decreasing effect with decreasing frequency.

10. A directive antenna system for a broad band of short wavescomprising an elongated signal collector connected at one end to highfrequency apparatus and the other end directed toward another stationwith which communication is to be established, said collector beingdivided into separate sections, phase changing networks interposedbetween each of two successive sections for producing therealong areversal in phase of the highest frequency energy in said band, saidphase changing networks having progressively decreasing effect withdecreasing frequency and means for preventing reflection of energy atsaid other end, said means having a resistance equal to the surgeimpedance of said antenna,

11. A directive antenna system for a broad band of short wavescomprising an elongated signal collector connected at one end to highfrequency apparatus and the other end directed toward another stationwith which communication is to be established, said collector beingdivided into separate sections, phase changing networks interposedbetween each two successive sections for producing therealong a reversalin phase of the highest frequency energy in said band, said phasechanging networks having progressively decreasing effect with decreasingfrequency, means for preventing reflection of energy at said other end,said means having a resistance equal to the surge impedance of saidantenna, said networks having a low and constant attenuation for allfrequencies within said band.

MARTIN KATZIN.

